Flexible arch-shaped corrugated structure

ABSTRACT

A flexible arch-shaped corrugated structure includes a plastic structure that can be light weight and easy to handle, while at the same time having suitable strength for carrying loads. By suitably engineering the corrugations, the need for structural ribs can be eliminated and thinner sidewalls can be used. The structure can include a series of vertically-oriented arched corrugations having surfaces that convexly arch or curve upwardly as well as laterally. Having both upward and lateral arched or curved features on the corrugations can provide increased strength to the corrugations and the structure. In a particular embodiment, the plastic structure is a leaching chamber. The structure can include access or inspection port structures disposed at the ends of the structure. The ports are dimensioned to mate with the opposing port of a like structure. In particular, the mated structures can articulate or rotate about the mated ports.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/707,490, filed on Aug. 10, 2005 (Attorney Docket No. 1652.2004-000),the teachings of which are incorporated herein by reference in itsentirety.

BACKGROUND

Arch-shaped corrugated structures are useful for various applications,particularly where the structure is exposed to load forces. A typicalapplication is a leaching chamber that can fabricated from athermoplastic, such as high density polyethylene (HDPE). The leachingchamber is typically injection molded into its shape.

Plastic leaching chambers are typically connected together in a seriesor an array and buried in a leaching field for dispersing waste water,sewage effluent, or storm water into the ground. The buried leachingchamber must resist loads from the overhead soil and possibly vehiculartraffic.

Prior art leaching chambers are typically rigid structures. Thicksidewalls, plastic structural ribs, and other features, are generallyused to increase the strength of the leaching chambers. That rigiditycan cause the leaching chambers to fail prematurely. Indeed, many priorart chambers break during shipment or transport to the installationsite, and during installation itself.

Leaching chambers are generally installed in accordance with state andlocal laws and regulations, as well as local customs. In particular,those laws, regulations, and customs dictate the width of the leachingfield trench, and thus limit the width of the leaching chamber,generally to either 36 inches, 24 inches, or 18 inches. Most leachingchambers are between about five to six feet in length to be dimensionedand light enough for an individual worker to handle.

SUMMARY

Particular embodiments of a flexible arch-shaped corrugated structureinclude a plastic structure that can be light weight and easy to handle,while at the same time having suitable strength for carrying loads. In aparticular embodiment, the plastic structure is a leaching chamber.

Prior art plastic leaching chambers have relied on thick sidewalls andstructural ribs to strength the structure. The ribs, however, can placeportions of the structure under tension when loaded and have been foundto introduce failure points into the structure. Failures at those pointstend to crack and propagate through the structure's wall to tear thestructure. Based on the locations of prior art ribbing, those failurestend to occur at the sidewalls.

Weight reductions can be realized by reducing the amount of structuralribs and decreasing the wall thickness. However, those weight-savingmeasures can decrease the strength of the leaching chamber.

By suitably engineering the corrugations, the need for structural ribscan be eliminated and thinner sidewalls can be used. Once installed, theflexible structure is strong but light. The resulting structure willflex before failing. When loaded, the structure is under compression.When failure does occur, the structure will fail at the crest of thecorrugations by buckling, not at the sidewalls. In addition to flexingbefore failing, a flexible structure is better able to cover unevenground.

Aspects of the invention include a structure having a base with an openbottom. The structure can be a chamber, and more particularly anarch-shaped leaching chamber. Also included are methods of fabricatingthe structure, such as by injection molding.

The structure can include a plurality of alternating corrugationsrunning along the structure's body, with each corrugation being archshaped about a center longitudinal axis with the bottom of the archbeing at the base and the crest of the arch being perpendicular to thebase. Furthermore, the corrugations can include a peak corrugationhaving a radius when sectioned through the center longitudinal axis,with the radius varying along the arch from the base to the crest of thearch.

The structure can include a series of vertically-oriented archedcorrugations having surfaces that convexly arch or curve upwardly aswell as laterally. Having both upward and lateral arched or curvedfeatures on the corrugations can provide increased strength to thecorrugations and the leaching chamber.

In particular embodiments, the radius is larger at the base than at thepeak of the arch. The larger corrugation portion at the bottom canprovide greater strength for resisting backfill. More particularly, theradius of the sectioned peak corrugation can be continuously variablealong the arch from the base to the peak. The radius blends into theside walls of the corrugations, which can be slightly angled forstrength purposes.

The structure's corrugations can be fabricated from plastic. Inparticular, the corrugations can have a wall thickness of less thanabout 0.1 inches and are not connected with structural ribs. The wallthickness can further be relatively uniform, with the variation inthickness being less than 10%.

The peak corrugations can include openings to facilitate the flow of aflowable medium, such as air, storm water, or sewage effluent betweenthe inside of the structure and the outside of the structure. The peakcorrugations can further include louvers to define the openings and toinhibit the intrusion of external material, such as soil, into thestructure. The louvers can, in particular, be formed as protrusions onthe peak corrugations. The louvers can include louvers with louvermembers that laterally extend across the laterally curving surfaces ofthe corrugations, resulting in laterally oriented arched louver members.In particular, the louvers can be formed to include a frame structureformed on the peak corrugations, the louvers being within the framestructure. The lateral arch of the louver members on the laterallycurving surfaces of the corrugations can also have increased strengthfor resisting the lateral thrust of backfill and can have increasedleaching surface area, in comparison to louvers that are merelystraight.

The corrugations can include valley corrugations or troughs betweenadjacent peak corrugations. Each valley corrugation can also have aplurality of formed louvers defining openings along a portion of thevalley corrugations.

In addition, a plurality of the valley corrugations can include a pairof stacking features. Each stacking feature can include a stackingcolumn extending vertically downward from the valley corrugation and astacking pocket above the valley corrugation and vertically aligned withthe stacking column. The stacking feature can further include a railtransitioning the stacking pocket to the top of the valley corrugation.

The structure (in particular a leaching chamber) can further include atleast one inspection port formed in the body. In one embodiment, theinspection port can be disposed at the crest of a valley corrugation.

The ends of the structure can include end flanges that can be overlappedand locked with end flanges on adjacent leaching chambers. The endflanges can be generally arched shaped in a vertical orientation. Oneend flange on a chamber can include an upwardly extending post, and theopposite end flange can include a mating downwardly facing socket forproviding pivotal engagement between adjacent leaching chambers. Theside walls of the end flanges can have a curved or tapered contour toallow the end flanges to slide over each other during lateral pivotingof the leaching chambers relative to each other. In some embodiments,the end flanges can have a curved contour forming a dome like structure,resulting in a post and dome locking feature.

The mating ends of the chambers can include access or inspection ports,which can be circular in shape and function as post and dome structuresdisposed at the crests of the ends. That is, mated leaching chambers canarticulate or rotatably pivot about the inspection port structureswithin a fixed range of angles. By positioning the inspection ports atthe ends of the leaching chamber, a potential structural weakness at thecorrugations can be removed and disposed at the end joint that can bestiffened through overlapping.

A plurality of arch-shaped structures can be joined into a series or anarray of structures. In particular, leaching chambers can be joinedtogether to form a leaching field.

A particular leaching field can include a first leaching chamber and asecond leaching chamber, which may be alike. Each leaching chamber canhave like end flanges, the end flanges including a first end flangehaving a first inspection port structure and a second end flange havinga second inspection port structure. The first leaching chamber is matedwith the second leaching chamber such that the first inspection portstructure of the first leaching chamber overlaps the second inspectionport structure of the second leaching chamber. At a particular joint,the first inspection port structure and the second inspection portstructure are opened to allow access to the interior of the leachingfield.

In addition, the longitudinal axis of the first chamber can be at anangle relative to the longitudinal axis of the second chamber. Morespecifically, the first and second leaching chambers can rotationalpivot about the mated inspection port structures.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention, including various novel details of construction andconstruction of parts, will be apparent from the following moreparticular drawings and description of embodiments, in which likereference characters refer to the same parts throughout the differentviews. The drawings are not necessarily to scale, emphasis instead beingplaced upon illustrating the principles of the invention. It will beunderstood that the particular details embodying the invention are shownby way of illustration only and not as a limitation of the invention.The principles and features of this invention may be employed and variedin numerous embodiments without departing from the scope of theinvention.

FIG. 1 is a perspective view of a particular leaching chamber.

FIG. 2 is a top view of the leaching chamber of FIG. 1.

FIG. 3 is a first end view of the leaching chamber 1 of FIG. 1.

FIG. 4 is a right side view of the leaching chamber 1 of FIG. 1.

FIG. 5 is a second end view of the leaching chamber 1 of FIG. 1.

FIGS. 6A-6B illustrate the interconnection of adjacent leaching chambersof FIG. 1.

FIG. 7 is a cross-sectional view along line A-A of FIG. 4.

FIG. 8 is a foreshortened cross-sectional view along line B-B of FIG. 4.

FIG. 9A is a load/defection curve for a commercial embodiment of theleaching chamber of FIGS. 1-8.

FIG. 9B is a load/defection curve for a competitor'scommercially-available Quick 4 leaching chamber.

FIG. 10 is a perspective view of a leaching chamber having inspectionport ends.

FIG. 11 is a side view of the leaching chamber 100 of FIG. 10.

FIG. 12 is a top view of the leaching chamber 100 of FIG. 10.

FIGS. 13A-13B illustrate the interconnection of adjacent leachingchambers of FIG. 10.

FIG. 14 is a cross-sectional diagram of nested chambers taken along lineC-C in a valley corrugation of FIG. 4.

DETAILED DESCRIPTION

In a particular embodiment of the invention, the flexible arch-shapedcorrugated structure is a plastic leaching chamber, which has an openbottom and louvered opening side walls for dispersing effluent frominside the structure to the ground. Leaching chambers can also be usedto disperse storm water. Similar structures can be used in otherapplications as well, including grain aeration and fish channels. Inother application, the side walls may not have louvered openings, suchas in culverts.

FIG. 1 is a perspective view of a particular leaching chamber. Theleaching chamber 1 has an open bottom and is generally arch shaped witha center axis 5. The chamber has a total length TL, a width W, and aheight H. The leaching chamber 1 includes a first end flange 10 at afirst end and a second end flange 20 at a second end. The first andsecond end flanges 10, 20 are complementary so that the first end flange10 of one chamber can mate with the second end flange 20 of an adjacentchamber to form a serial chain of chambers for a leaching field asunderstood by those of ordinary skill in the art.

In particular, the ends of the leaching chamber can include end flangesthat can be overlapped and locked with end flanges on adjacent leachingchambers. The end flanges 10, 20 are generally arched shaped in avertical orientation. As shown, the end flanges 10, 20 feature a postand dome interconnect, which is described in more detail in U.S. DesignPat. No. 403,047, issued on Dec. 22, 1998 to Gray, the teaching of whichare incorporated herein by reference. A post structure 12 is located atthe crest of the first end flange 10 and a dome structure 22 is locatedat the crest of the second end flange 20. Thus, the second end flange 20overlaps the first end flange 10 of adjacent chambers. The first endflange 10 also includes latching grooves 14 and the second end flange 20includes a lip structure 24.

A base flange 30 acts as feet for the leaching chamber 1. Wheninstalled, the base flange is set on the surface of a prepared trench.An elevated flange 32 is fabricated on the base flange 30 adjacent tothe first (overlapped) end flange 10. When two like chambers are mated,the base flange 30 adjacent to the second (overlapping) end flange 20 isreceived in the gap under the elevated flange 32.

The leaching chamber 1 also includes a plurality of alternating peakcorrugations 40 and valley corrugations or troughs 50 along its length.The corrugations 40, 50 include respective sidewalls 45, 55 with openinglouver features 140 having a height h for dispersing effluent or stormwater from inside the chamber 1. The distal louvered corrugations areconnected to the respective end flanges 10, 20 via a first endtransition corrugation 15 and a second end transition corrugation (notshown).

The louver features 140 are formed onto and follow the profile of thecorrugations 40, 50. In particular the amount of material absent fromthe corrugation sidewalls due to the louver slots is replaced by astructural louver frame. In contrast, prior art louvers are generallyformed by simply perforating the sidewall, which introduces a structuralweakness in the corrugations.

Also shown is an inspection port 60 located at the crest of a valleycorrugation. When a leaching field is installed, selected inspectionports 60 can be cut out for later access. It should be understood thatthe number and position of access ports can be a design choice.

FIG. 2 is a top view of the leaching chamber 1 of FIG. 1. The layinglength LL of the chamber is defined as the longitudinal distance betweenthe centers of the post structure 12 and the dome structure 22. Thisview better illustrates the first end transition corrugation 15 and thesecond end transition corrugation 25. Also note that the corrugations donot have a fixed contour. Also note that there is no external ribbingbetween corrugations, as is frequently used in prior art leachingchambers. Internal ribbing between corrugations is also not used.

This view also illustrates tabs 34 on the second end of the base flange30. As will be illustrated below, the structure of the ends permitsinterconnected chambers to articulate or swivel a through a small angleso that a series of interconnected chambers can follow a non-linearpath. Other swivel connectors can also be used, such as those describedin U.S. Pat. No. 6,592,293 to Gray, U.S. Pat. No. 6,592,293 to Hedstromet al. and in co-pending U.S. application Ser. No. 10/619,060 byHedstrom et al., the teachings of which are incorporated herein byreference in their entirety. Of course, non-swivel connecting joints canalso be employed.

The latching grooves 14 on the first end flange 10 and the lip 24 on thesecond end flange 20 are used to connect end caps to terminate a seriesof chambers.

FIG. 3 is a first end view of the leaching chamber 1 of FIG. 1. Inaddition to illustrating the arch shape along the center line 5 and thepost connector structure 12, details of the peak corrugation louvers 140are shown. Note that the louvers 140 include louver members 142 a, 142b, . . . , 142 y, 142 z. Those louver members protrude from thecorrugation side wall.

FIG. 4 is a right side view of the leaching chamber 1 of FIG. 1. Thisview further illustrates the contours of the corrugations and details ofthe ends.

As shown, the leaching chamber 1 includes a series ofvertically-oriented arched corrugations having surfaces that convexlyarch or curve upwardly as well as laterally. The side walls of theleaching chamber between the corrugations can include louvers forallowing the passage of liquids from the leaching chamber. In addition,the corrugations can also include louvers with louver members thatlaterally extend across the laterally curving surfaces of thecorrugations, resulting in laterally oriented arched louver members.

Having both upward and lateral arched or curved features on thecorrugations can provide increased strength to the corrugations and theleaching chamber. The corrugations can have sidewalls having flatsurfaces. The lateral arch of the louver members on the laterallycurving surfaces of the corrugations can also have increased strengthfor resisting the lateral thrust of backfill and can have increasedleaching surface area, in comparison to louvers that are merelystraight.

FIG. 5 is a second end view of the leaching chamber 1 of FIG. 1. Inaddition to illustrating the arch shape along the center line 5 and thedome connector structure 22, details of the peak corrugation louvers 140are shown. As shown in FIG. 3, the louvers 140 include louver members142 a, 142 b, . . . , 142 y, 142 z. Again, those louver members protrudefrom the corrugation side wall.

FIGS. 6A-6B illustrate the interconnection of adjacent leaching chambersof FIG. 1. As shown a first chamber 1A and a second chamber 1Binterconnect by overlapping end flanges. As shown in FIG. 6A, the firstchamber 1A is installed in place with its first end flanges 10A exposed.The second chamber 1B is installed by placing its second end flange 20Bover the first end flange 10A of the first chamber 1B, with the domestructure 22B aligned over the post structure (not shown) of the firstchamber 1A. Note that the second chamber 1B is elevated at a verticalangle. As shown in FIG. 6B, the interconnection is completed by tiltingthe second chamber 1B down so that the second chamber base flange 30B isreceived under the elevated flange 32A of the first chamber 1A. Notethat the joint, particularly the gap below the elevated flange 32A,allows for articulated movement of the connected chambers. Latches orother suitable engageable structures on the ends of the leachingchambers can be used to help hold the mated chambers together.

Although two like leaching chambers 1A, 1B are shown being mated, otherstructures can also be mated with a leaching chamber. For example, oneor more angle couplers, similar to those described in theabove-referenced U.S. Pat. No. 6,592,293 to Hedstrom et al., can beserially attached to a leaching chamber.

FIG. 7 is a cross-sectional view along line A-A of FIG. 4. Thisillustrates a typical peak corrugation louver structure 140 and valleycorrugation louver structure 52 of FIG. 1. Referring to the peakcorrugation louver structure 140, a base louver 142 a transitions intothe base flange 30 and a top louver 142 z extends from the maincorrugation sidewall. Between the base louver 142 a and the top louver142 z are a plurality of interior louvers, of which the two adjacent tothe base louver 142 a and the top louver 142 z are shown. The louvers140 are designed to allow flow of effluent or storm water from withinthe chamber and to inhibit backfill from entering the chamber.

The first louver 142 a and the interior louvers 142 b, 142 y includes arespective lip 144 a, 144 b, 144 y along the inside of their topsurfaces 146 a, 146 b, 146 y. The top louver surfaces 146 run parallelto the base flange 30. The lips 144 extend above the top louver surface146 by a first distance d1 and are separated from the next louver by asecond distance d2.

The bottom surfaces 48 of the interior louvers 142 b, 142 y and the toplouver 142 z run at an angle Θ1 relative to the adjacent top louversurfaces 146 a, 146 y. The bottom surfaces 148 are thus separated fromthe prior louver top surface 146 by a third distance d3. The interiorlouvers have an inside height of d4, including the lip, and an outsideheight of d5. As shown, the louvers have an inside-to-outside width d6,which is greater than the thickness of the side wall.

In a specific embodiment, the chamber wall thickness is nominally 0.10inches. For the louvers, d1 is 0.030 inches, d2 is 0.110 inches, d3 is0.152 inches, d4 is 0.130 inches, d5 is 0.083 inches, d6 is 0.250 inches(including the sidewall thickness) when measured perpendicular to thearch, and Θ1 is 4.0 degrees. Other dimensions can be substituted to meetother engineering requirements. For example, although the louversurfaces is offset and extends from the corrugation side walls by about0.15 inches, other approaches to the infiltration structures could beused.

FIG. 8 is a foreshortened cross-sectional view along line B-B of FIG. 4.The view shows a representative horizontal cross-section of a peak andvalley corrugation.

The particular arc of the peak corrugation 40 is continuously variablefrom the bottom of the corrugation to the crest. The peak corrugationis, in particular, a linear blended surface between the horizontal plane(at the base flange 30) and the vertical plane (at the crest of thechamber arch). More specifically, the arc is only measurable as a radius(but still variable) if the corrugation is sectioned perpendicular tothe chamber's arch. In the illustrated view, the curve is an incidentalellipse. Also, when sectioned horizontally as shown, the thickness ofthe louvers is variable. If a cross-section were taken perpendicular tothe chamber arch (i.e. passing through the center axis 5 (FIG. 1)), thenthe louver thickness would be equal to d6 (FIG. 7).

The laterally curving surfaces of the corrugations has a radius thatbecomes smaller with an increase in elevation, starting at the bottom ona lateral plane and ending at the top on a vertical plane. That changein dimensions results in corrugations having portions that are larger atthe bottom and smaller at the top. The larger corrugation portion at thebottom can provide greater strength for resisting backfill. The radiusblends into the side walls of the corrugations, which can be slightlyangled for strength purposes. Again, note that the louvers protrudedfrom the corrugations.

Particular chambers can have a peak corrugation profile that is similarto a successful pipe profile disclosed on U.S. Pat. No. 6,644,357 toGoddard, the teachings of which are incorporated herein by reference.Unlike a pipe, however, the chamber does not require a fixed diameter.Instead, the particular peak corrugations have an arch-shape that islarger in diameter at the base than at the crest.

As shown in FIG. 8, the peak corrugations 40 and the valley corrugations50 have respective louvered opening features 140, 150. Note that thelouver features is a formed feature that follows the contour of thecorrugations. This shaping of the louvers increases the amount of openarea provided at the corrugations.

At the peak corrugation 40, the louver feature 140 includes a protrudingframe 148 and center support member 149. In particular, the approximateamount of sidewall material removed to form the open areas between thelouvers in the peak corrugation is replaced by material in the frame 148and center support 149. The valley corrugations 50 have similar louverfeatures 150. Although the valley corrugations 50 have center supports159, outer support is provided by the sidewall itself 158. Also shown isa brace 157 for base of the valley louver center support 159. In aparticular embodiment, the frame 148 and center supports 149, 159 have athickness equal to the thickness of the louvers, d6 (FIG. 7).

In a particular embodiment of the above-described leaching chamber 1,the leaching chamber has a total length (TL) of 63.16 inches, a layinglength (LL) of 60.00 inches, a width (W) of 34.50 inches, a height (H)of 13.00 inches, and a height to the highest louver opening (h) of 7.13inches. The overall chamber weighs about 15.3 pounds. With respect tothe above-referenced U.S. Pat. No. 6,644,357, the peak corrugations havea 36-inch pipe profile at its base and transitions to a 24-inch pipeprofile at its crest.

Further dimensions are given in Table 1, below. TABLE 1 Chamber Volume(Lay Length) 13896.4 Sq. In. Total Bottom Area 2070.00 Sq. In. OpenBottom Area 1747.32 Sq. In. Footprint Area 322.68 Sq. In. SidewallInfiltration Surface Area 462.77 Sq. In. Chamber Volume per Linear Foot2779.28 Cu. In. Total Bottom Area per Linear Foot 414.00 Sq. In. OpenBottom Area per Linear Foot 349.46 Sq. In. Footprint Area per LinearFoot 64.54 Sq. In. Sidewall Infiltration Surface Area per Linear Foot92.55 Sq. In. Total Infiltration Surface 442.02 Sq. In.

A leaching chamber manufactured in accordance with the above disclosure(ARC-36 H-10) has been compared with samples of other low-weightcommercially-available leaching chambers. The results between the ARC-36H-10 embodiment and the Quick 4 chamber from Infiltrator Systems, Inc.are summarized in Table 2, below: TABLE 2 ARC-36 H-10 Quick 4 LL × W × H60.0 × 35.5 × 12.5 46.5 × 33.5 × 13.0 inches inches Weight (lbs)   15.3  12.5  3% Deflection 1320 lbs 254 lbs  6% Deflection 3446 lbs 1015 lbs12% Deflection 5573 lbs 5287 lbs 25% Deflection 2573 lbs 3247 lbsMaximum Load 5573 lbs 6509 lbs Failure Point 12.0% 19.6% SidewallThickness 0.091-0.099 inch 0.092-0.106 inch RangeNote that the disclosed ARC-36 chamber resists loads much better thanthe competing products. It requires 5 times the load of the Quick 4chamber to deflect 3% and over 3 times the load to deflect 6%.For the ARC-36, the first failure point occurs when the crown buckles.In the Quick 4 product, there are preliminary failures before thechamber fails. The distinctions are illustrated by load/deflectioncurves.

FIG. 9A is a load/defection curve for the ARC-36 chamber of Table 2. Thecurve was plotted from actual measurement data. Note that up until thefailure point A1 at 5573 pounds, the load/deflection curve is smooth.Even after the failure point, the curve remains smooth before levelingoff. This indicates that, even after buckling, the chamber remains as aintegral structure.

FIG. 9B is a load/deflection curve for the Quick 4 chamber of Table 2.Again, the curve was plotted from actual measurement data. The Quick 4chamber fails at a load of 6509 pounds at point Q1, but there is anearlier break at about 5500 pounds at point Q2. After the main failure,the curve falls off sharply and reveals further breaks at least atpoints Q3, Q4, Q5, Q6, and Q7, indicating that the chamber has loststructural integrity.

While the above-disclosed leaching chamber operates well for itsintended purpose, it requires a trench width of at least 36 inches. Somelocalities require narrower trenches, such as 24 inches or 18 inches. Asnarrow chambers where designed, it was found that the location of theinspection port in the body of the chamber tended to weaken the chamber.To solve that problem, the inspection port was moved from the body ofthe chamber to the ends.

FIG. 10 is a perspective view of a leaching chamber having inspectionport ends. Like the leaching chamber 1 of FIGS. 1-8, the leachingchamber 100 has an open bottom and is generally arch shaped with acenter axis 105. The chamber has a total length TL′, a width W′, and aheight H′. The leaching chamber 100 includes a first end flange 110 at afirst end and a second end flange 120 at a second end. The first andsecond end flanges 110, 120 are complementary so that the first endflange 110 of one chamber can mate with the second end flange 120 of anadjacent chamber.

The first end flange 110 includes a first inspection port structure 112at the crest of the arch and the second end flange 120 includes a secondinspection port 122 at the crest of the arch. Access to the interior ofan installed leaching field is attained by cutting out one of moreinspection ports. It should be recognized that the first inspection port112 functions as a post and the second inspection port 122 functions asa dome in a post-dome configuration. That is, when two chambers aremated, the second inspection port 122 of one chamber overlaps the firstinspection port 112 of another chamber.

Because the inspection ports are circular structures, the mated chamberscan pivot about the mated inspection ports 112, 122 though a fixedangular range.

FIG. 11 is a side view of the leaching chamber 100 of FIG. 10. Exceptfor structural differences to accommodate the inspection ports, thechamber 100 is similar to the chamber 1 of FIGS. 1-8. The laying lengthLL′ of the chamber is defined as the longitudinal distance between thecenters of the first inspection port 112 and the second inspection port122.

Note that the inspection port structure 112 at the first end is disposedon a larger length first end flange 110 as compared to the leachingchamber of FIG. 1. That additional span if repeated at the opposite endcould introduce a weakness into the joint. To counteract thatpossibility, there is a peak corrugation at the second end that isintersected by the second inspection port structure 122. Thatcorrugation adds strength to the joint without the need for a structuralrib.

FIG. 12 is a top view of the leaching chamber 100 of FIG. 10. Note thatthe first end 132 of the base flange 130 is contoured to receive asecond end 134 of another base flange 130. The received second end isheld in place by tabs 116 extending from the first end flange 110.

FIGS. 13A-13B illustrate the interconnection of adjacent leachingchambers of FIG. 10. Note that assembly is similar to that shown inFIGS. 6A-6B, except that the post 12 is replaced by a first (overlapped)inspection port 112 and the dome 22 is replaced by a second(overlapping) inspection port 122. To access the interior of thechamber, the mated inspection ports 112, 122 are cut out.

In a particular embodiment of the above-described leaching chamber 100,the leaching chamber has a total length (TL′) of 67.25 inches, a layinglength (LL′) of 60.00 inches, a width (W) of 22.00 inches, a height (H)of 11.623 inches. Note that the resulting 22-inch chamber is nearly astall as the previously described 36-inch chamber, which results in amore favorable arch profile.

It should be understood that the dimensions given above are approximateor nominal dimensions, which can vary due to changes in materialproperties or manufacturing techniques. The performance of themanufactured product can be enhanced by designing for even distributionof plastic throughout the part. In a particular embodiment, the actualsidewall thickness varies by less than 10% of the maximum thickness.

The chambers are typically shipped from a factory to a distributioncenter by being stacked on pallets. It is advantageous to stack manychambers on a single pallet. The rigidity of prior art leaching chamberscan cause breakage during transport. It is not unusual for 10% of priorart chambers on a pallet to be cracked during shipment. The flexibilityand profile of the above-disclosed chambers allows them to be morereliably transported, and in greater numbers per pallet.

FIG. 14 is a cross-sectional diagram of nested chambers taken along lineC-C in a valley corrugation of FIG. 4. As shown, two chambers 1A, 1B arestacked, such as for shipping or storage. Each valley corrugationincludes a pair of stacking columns 162A, 162B extending downward fromthe underside of the corrugation and a pair of stacking pockets 164A,164B on the topside of the corrugation. As shown, the stacking columns162A, 162B are tube shaped and can be longer than the distanceseparating the surface of the peak corrugations from the surface of thevalley corrugations. The stacking pockets 164A, 164B are delimited fromthe corrugation surface by a rail 166A, 166B formed into thecorrugation. When stacked, the bottom of the top stacking column 162Brests in a respective pocket 164A of the next lower chamber 1A, with therail 166A guiding and holding the column 162B in the pocket 164A.

Because the arch shape and corrugations decrease in size away from thebase, the chambers can be closely stacked. The stacking pockets 164guide the columns 162 so that they are vertically aligned. With a palletsuitably constructed to transfer the column load to the pallet, a stackof at least 60 chambers can be shipped without damage. Even if the loadis not directly transferred, the only chamber that typically suffersdamage is the bottom chamber, which carries the load of all chambersabove it, and generally only when the plastic is exposed to sufficientheat to weaken its stacking pocket 164.

The flexibility of the above-disclosed chambers also reduces the risk ofdamage due to rough handling of individual chambers. Instead ofresisting twisting and bending forces, which can break prior artchambers, the above-disclosed chambers move with the forces by flexing.While the corrugations themselves are strong, the chamber can flexaround its center axis. In particular, the chamber can be easily twistedso that the opposing ends are at about 45 degrees relative to eachother. Once the forces are removed, the chamber returns to its nominalshape.

While particular embodiments of the leaching chambers are injectionmolded from high density polyethylene (HDPE), other manufacturingtechniques can be used. In addition, the leaching chambers can befabricated from another suitable polymer, such as polypropylene, oranother material, such as concrete, metal, or ceramics, or combinationsof materials.

While this invention has been shown and described with references toparticular embodiments, it will be understood by those skilled in theart that various changes in form and details may be made to the detailedembodiments without departing from the scope of the invention as definedby the appended claims.

1. A structure having a base with an open bottom, comprising: aplurality of alternating corrugations, each corrugation being archshaped about a center longitudinal axis with the bottom of the archbeing at the base and the crest of the arch being perpendicular to thebase; and the corrugations including a peak corrugation having a radiuswhen sectioned through the center longitudinal axis, the radius varyingalong the arch from the base to the crest of the arch.
 2. The structureof claim 1 wherein the radius is continuously variable along the archfrom the base to the peak.
 3. The structure of claim 1 wherein theradius is larger at the base than at the peak of the arch.
 4. Thestructure of claim 1 wherein the peak corrugation includes an opening tofacilitate the flow of a flowable medium between the inside of thestructure and the outside of the structure.
 5. The structure of claim 4wherein the peak corrugation further includes louvers to define theopenings and to inhibit the intrusion of external material into thestructure.
 6. The structure of claim 1 wherein the corrugations areplastic.
 7. The structure of claim 1 wherein the corrugations are notconnected with structural ribs.
 8. The structure of claim 1 wherein thecorrugations have a wall thickness of about 0.1 inches.
 9. A corrugatedplastic chamber having a base with an open bottom, comprising: anarch-shaped plastic body having a length and opposing ends; a pluralityof alternating corrugations running along the length of the body, eachcorrugation being arch shaped about a center longitudinal axis with thebottom of the arch being at the base and the crest of the arch beingperpendicular to the base; and the corrugations including a plurality ofpeak corrugations, each having a radius when sectioned through thecenter longitudinal axis, the radius varying along the arch from thebase to the crest of the arch.
 10. The chamber of claim 9 wherein theradius is continuously variable along the arch from the base to thepeak.
 11. The chamber of claim 9 wherein the radius is larger at thebase than at the peak of the arch.
 12. The chamber of claim 9 whereineach of the peak corrugations includes an opening to facilitate the flowof a flowable medium between the inside of the chamber and the outsideof the chamber.
 13. The chamber of claim 12 wherein each of the peakcorrugations further includes louvers to define the openings and toinhibit the intrusion of external material into the chamber.
 14. Thechamber of claim 9 wherein the corrugations are not connected withstructural ribs.
 15. The chamber of claim 9 wherein the corrugationshave a wall thickness of about 0.1 inches.
 16. The chamber of claim 9wherein the corrugations have a wall thickness that does not vary bymore than 10%.
 17. A leaching chamber for burial in the ground,comprising: an arch-shaped plastic body having a length and opposingends; a plurality of alternating corrugations running along the lengthof the body, each corrugation being arch shaped about a centerlongitudinal axis with the bottom of the arch being at the base and thecrest of the arch being perpendicular to the base; the corrugationsincluding a plurality of peak corrugations, each peak corrugationhaving: a radius when sectioned through the center longitudinal axis,the radius varying along the arch from the base to the crest of thearch; and a plurality of openings along a portion of the peakcorrugation.
 18. The leaching chamber of claim 17 wherein the radius iscontinuously variable along the arch from the base to the peak.
 19. Theleaching chamber of claim 17 wherein the radius is larger at the basethan at the peak of the arch.
 20. The leaching chamber of claim 17wherein the peak corrugation openings facilitate the flow of an effluentfrom the inside of the leaching chamber to the outside of the leachingchamber.
 21. The leaching chamber of claim 20 wherein the peakcorrugation further includes louvers to define the openings and toinhibit the intrusion of soil into the structure.
 22. The leachingchamber of claim 21 wherein the louvers formed on the peak corrugations.23. The leaching chamber of claim 22 further comprising a framestructure formed on peak corrugations, the louvers being within theframe structure.
 24. The leaching chamber of claim 17 wherein thecorrugations are not connected with structural ribs.
 25. The leachingchamber of claim 17 wherein the corrugations have a wall thickness ofabout 0.1 inches.
 26. The leaching chamber of claim 17 wherein thecorrugations have a wall thickness that does not vary by more than 10%.27. A leaching chamber for burial in the ground, comprising: anarch-shaped plastic body having a length and opposing ends; a pluralityof alternating corrugations running along the length of the body, eachcorrugation being arch shaped about a center longitudinal axis with thebottom of the arch being at the base and the crest of the arch beingperpendicular to the base, the corrugations including; a plurality ofpeak corrugations, each peak corrugation having: a radius when sectionedthrough the center longitudinal axis, the radius continually varyingalong the arch from the base to the crest of the arch, wherein theradius is larger at the base than at the crest; a plurality of formedlouvers defining openings along a portion of the peak corrugation; aplurality of valley corrugations between adjacent peak corrugations,each valley corrugation having a plurality of formed louvers definingopenings along a portion of the valley corrugations.
 28. The leachingchamber of claim 27 wherein the corrugations are not connected withstructural ribs.
 29. The leaching chamber of claim 27 wherein thecorrugations have a wall thickness of about 0.1 inches.
 30. The leachingchamber of claim 27 wherein the corrugations have a wall thickness thatdoes not vary by more than 10%.
 31. The leaching chamber of claim 27wherein a plurality of the valley corrugations includes a pair ofstacking features.
 32. The leaching chamber of claim 31 wherein eachstacking feature includes: a stacking column extending verticallydownward from the valley corrugation; and a stacking pocket above thevalley corrugation and vertically aligned with the stacking column. 33.The leaching chamber of claim 32 wherein the stacking feature furtherincludes a rail transitioning the stacking pocket to the top of thevalley corrugation.
 34. The leaching chamber of claim 27 furthercomprising at least one access port formed in the body.
 35. The leachingchamber of claim 34 wherein the access port is disposed at the crest ofa valley corrugation.
 36. The leaching chamber of claim 34 wherein thereare a pair of access ports, one access port at each end of the body. 37.A method of manufacturing a structure having a base with an open bottom,comprising: forming a plurality of alternating corrugations, eachcorrugation being arch shaped about a center longitudinal axis with thebottom of the arch being at the base and the crest of the arch beingperpendicular to the base; and forming the corrugations to include apeak corrugation having a radius when sectioned through the centerlongitudinal axis, the radius varying along the arch from the base tothe crest of the arch.
 38. A method of manufacturing a corrugatedplastic chamber having a base with an open bottom, comprising: formingan arch-shaped plastic body having a length and opposing ends; forming aplurality of alternating corrugations running along the length of thebody, each corrugation being arch shaped about a center longitudinalaxis with the bottom of the arch being at the base and the crest of thearch being perpendicular to the base; and forming the corrugations toinclude a plurality of peak corrugations, each having a radius whensectioned through the center longitudinal axis, the radius varying alongthe arch from the base to the crest of the arch.
 39. A method ofmanufacturing a leaching chamber for burial in the ground, comprising:forming an arch-shaped plastic body having a length and opposing ends;forming a plurality of alternating corrugations running along the lengthof the body, each corrugation being arch shaped about a centerlongitudinal axis with the bottom of the arch being at the base and thecrest of the arch being perpendicular to the base; forming thecorrugations to include a plurality of peak corrugations, each peakcorrugation having: a radius when sectioned through the centerlongitudinal axis, the radius varying along the arch from the base tothe crest of the arch; and a plurality of openings along a portion ofthe peak corrugation.
 40. A method of manufacturing a leaching chamberfor burial in the ground, comprising: forming an arch-shaped plasticbody having a length and opposing ends; forming a plurality ofalternating corrugations running along the length of the body, eachcorrugation being arch shaped about a center longitudinal axis with thebottom of the arch being at the base and the crest of the arch beingperpendicular to the base, the forming of the corrugations including;forming a plurality of peak corrugations, each peak corrugation having:a radius when sectioned through the center longitudinal axis, the radiuscontinually varying along the arch from the base to the crest of thearch, wherein the radius is larger at the base than at the crest; aplurality of formed louvers defining openings along a portion of thepeak corrugation; forming a plurality of valley corrugations betweenadjacent peak corrugations, each valley corrugation having a pluralityof formed louvers defining openings along a portion of the valleycorrugations.